Construction Machine, As Well As Clutch For Switching The Power Flow

ABSTRACT

Construction machine, with working drum mounted at a machine frame, combustion engine for driving the working drum, drive train between the combustion engine and the working drum, and clutch in the drive train, where the clutch is arranged between a drive shaft and output shaft of the drive train, clutch elements on drive side capable of being engaged with clutch elements on output side, where clutch elements on the drive side or on output side are provided with several clutch part elements that are permanently engaged with one another via at least one mechanical coupling, it is provided that a braking device acting between the drive shaft and the output shaft is arranged at the clutch, said braking device being additionally engaged during engagement of the clutch in order to eliminate or reduce any rotary vibrations caused by play of mechanical coupling between clutch part elements.

BACKGROUND OF THE INVENTION

The invention relates to a construction machine, as well as a clutch fora construction machine.

Such construction machines are known, for example, from WO 02/01005. Thecombustion engines of the newer generation, in particular dieselengines, used in such construction machines generate rotary vibrationsof significant proportions due to the lightweight design. This resultspartly from the fact that light components, in particular lightcrankshafts and flywheels, are increasingly used, and from the fact thatthe combustion process happens differently as a result of alteredignition times and injection times due to exhaust emission stipulations,which leads to the generation, to an increasing extent, of rotaryvibrations in the output train.

The significant extent of rotary vibrations creates problems, however,with downstream drive mechanisms in the drive train like, for instance,with downstream clutches and gearboxes. These rotary vibrations canintensify even further in such clutches and gearboxes due to mechanicalcouplings, in particular form-fitting couplings, that have play.Material fatigue, as well as wear and tear can increase considerably,which can lead to a reduced service life of the elements in the drivetrain. In the process, a progressive reinforcement effect can beobserved, because wear and tear caused by these damaging vibrationsinevitably leads to increased play, by which the vibrations are in turnreinforced. This problem exists in construction machines in general, andin particular in automotive road milling machines, stabilizers orrecyclers, as well as in crushing plants, for example, jaw crushers orimpact crushers.

SUMMARY OF THE INVENTION

It is an objective of the present invention to create a constructionmachine and a clutch in which wear and tear of the drive train elements,and in particular the clutch, due to the unwanted rotary vibrations isreduced in an advantageous manner.

The invention provides in an advantageous manner that a braking deviceacting between the drive shaft and the output shaft is arranged at theclutch, the braking device being additionally engaged, or capable ofbeing engaged, during engagement of the clutch, in order to eliminate orto reduce any rotary vibrations that are due to play of the mechanicalcoupling between the part elements of the clutch.

The invention permits in an advantageous manner to damp or to eliminatethe rotary vibrations generated at the clutch.

The braking device may be capable of being additionally engagedimmediately prior to, during or after switching of the clutch, and maythen be engaged until separation of the engagement of the clutch. Thebraking device causes the part elements of the clutch, within theinevitably existing play of the mechanical coupling of the same, to restagainst one another in the direction of the driving torque, and to befixed in this position by the braking device, so that the toothings ofthe part elements of the clutch cannot vibrate to and fro in relation toone another within the existing play in case of a non-load operation,i.e. in idle operation, when the clutch is switched and without a loadtorque at the output shaft. In that way, wear and tear is avoided in thedrive train and in particular at the part elements of the clutch, sothat the service life of the clutch and other elements of the drivetrain is prolonged considerably.

The braking force generated by the braking device may be adjusted insuch a manner that the braking torque between the drive shaft and theoutput shaft resulting from the braking force is smaller than the loadtorque of the output shaft in working mode, and is larger than the dragtorque of the output shaft when the rotating working drum is not inworking mode.

It is preferably provided that the braking force couples the partelements of the clutch on the drive side or output side to one anotherin such a manner that the mechanical coupling is play-free at least inthe direction of the load operation, i.e. in the direction of thedriving torque. The braking torque is then smaller than the maximumtorque in the direction of the load, and larger than the maximum torquein the opposite direction (the difference torque from the two being thedrag torque of the drum), by way of which a single slipping-through towhere the part elements of the clutch rest against one another takesplace in the direction of the load, but slipping-through is avoided inthe opposite direction. If the braking torque is smaller than themaximum torque against the direction of the load, meaning smaller thanthe smaller one of the two torques, then slipping-through, and thus therotary vibration caused by the play of the mechanical coupling, cannotbe eliminated but can at least be reduced.

The braking force generated by the braking device may be adjusted insuch a manner that the braking torque between the drive shaft and theoutput shaft resulting from the braking force is larger than the maximumtorque occurring in the drive train in non-load operation. In that way,it is ensured that the elements of the mechanical coupling that haveplay remain in a position defined by the braking engagement at alltimes, as long as the operating mode of non-load operation is given.

It goes without saying that the braking device is of no effect for theoperation of the working drum under load, because the load torques arethen many times higher than the braking torque adjusted. In thisoperating mode, an effect of the braking device is also not requiredbecause the part elements of the clutch are pre-tensioned so stronglydue to the extremely high torques then being transmitted that anyvibrating of the part elements of the clutch against one another is notpossible.

The mechanical coupling between the part elements of the clutch on thedrive side or output side preferably consists of at least one toothing.

The braking device is provided with at least one brake lining, which isarranged at a clutch element of the clutch on the drive side and/or theoutput side. The adhesive friction of the brake lining is designed insuch a manner that, in non-load operation, the drive side of the clutchis coupled to the output side of the clutch in a practically rigidmanner. It is essential in this regard that no slippage can occur at thebraking device in non-load operation.

The braking device may be provided with an annular flange which iselastic in axial direction and, when in operation under friction lock,is engaged with an axial resting surface of a clutch element on thedrive side or output side.

Alternatively, the braking device may be provided with radially actingbrake linings that may interact with corresponding radial restingsurfaces of a clutch element on the drive side or output side.

In a preferred embodiment, it is provided that at least one part of thebraking device is arranged in a non-rotating manner at a movable part ofthe clutch elements on the output side. An axially movable pressurepiston on the output side that engages the friction linings of theclutch, for example, is suited to this purpose.

The braking device may be engaged with a front surface or acircumferential surface of a hollow ring that is coupled to the driveshaft or output shaft in a non-rotating manner and forms a part elementof the clutch.

A preferred embodiment provides that the movable clutch elements on theoutput side are capable of being operated hydraulically, and that theannular flange of the braking device is coupled to the hydraulic pistonfor the operation of the clutch.

In a radially acting braking device, the brake lining may be engagedthrough centrifugal forces during rotation of the output shaft.

An electromagnetic brake or an eddy current brake may be used as analternative braking device.

The drive train comprises, for example,

a clutch for switching the power flow,

a traction mechanism with drive elements and output elements,

a planetary gear for the working drum, and/or

an elastic coupling, and/or

a pump transfer case.

At least one vibration damper and/or vibration absorber may additionallybe arranged at the working drum or in the drive train down-stream of thecombustion engine, the said vibration damper and/or vibration absorberserving the purpose of eliminating or at least reducing any rotaryvibrations generated by the combustion engine.

The vibration damper and/or vibration absorber preferably consists of anelastomer-metal composite element. The vibration damper and/or vibrationabsorber may consist of an additional mass or vibrating mass arrangedcoaxially to that particular shaft in which the rotary vibrations of thecombustion engine are occurring, where the additional mass or vibratingmass is capable of being excited to rotary vibrations that counter-actthe rotary vibrations of the combustion engine because of inertia.

In the following, an embodiment of the invention is explained in moredetail with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a road construction machine.

FIG. 2 is a schematic depiction of a drive train in the roadconstruction machine.

FIG. 3 is a schematic side view of the drive train.

FIG. 4 is a clutch with braking device provided on the output side, aswell as with an optional vibration damper.

FIG. 5 is a section along the line V-V in FIG. 4.

FIG. 6 is the vibration damper of the clutch according to FIG. 4.

FIG. 7 is a clutch with radially acting braking device, vibrationdamper.

FIG. 8 is the radially acting braking device according to FIG. 7.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a construction machine 1 in the form of a large millingmachine with a machine frame 4 carried by a height-adjustable chassis 2,and a drive engine 10. A working drum 6 with tools consisting of millingbits for working a pavement surface is mounted at the machine frame 4.The working drum 6 is driven by a drive train 8. The drive train 8includes at least one traction mechanism 12.

FIG. 2 shows a schematic cross-section of a construction machine 1,namely in particular a road milling machine, a recycler or a stabilizerwith a working drum 6 that is mounted in a machine frame 4.Alternatively, the working drum 6 may be mounted in a drum housing thatis in turn firmly attached to the machine frame. The working drum 6 mayalso be mounted to pivot at a machine frame 4. The machine frame 4 iscarried by a chassis 2 that is depicted in FIG. 1. The working drum 6may consist of, for instance, a milling drum 6.

The drive engine 10 preferably consists of a diesel engine. Via anelastomer coupling 20, the combustion engine 10 may be coupled to a pumptransfer case 16 for driving hydraulic modules, for instance, hydraulicpumps 18. The elastomer coupling 20 may also be arranged at a differentplace within the drive train 8.

A traction mechanism 12 for the mechanical drive of the working drum 6is provided with a drive element 11 which is coupled to an output shaft22 in a non-rotating manner, and an output element 13 which is coupledto the drive shaft 15 of the working drum 6 in a non-rotating manner. Aplanetary gear 24 may additionally be arranged between the drive shaft15 and the working drum 6.

The traction mechanism 12 is preferably a belt drive, where the driveelements and output elements consist of belt pulleys 11, 13, withseveral drive belts 30 revolving around the belt pulleys 11, 13.Alternatively, the traction mechanism 12 may also consist of a chaindrive, with the drive elements and output elements then consisting ofsprockets.

The drive train 8 is further provided with a conventional device forswitching the torque, which is arranged in the drive train 8 between thedrive engine 10 and the working drum 6, and preferably consists of aclutch 14 of, for instance, the Planox® clutch type.

The drive engine 10 or the pump transfer case 16 respectively may becoupled to the belt pulley 11 on the engine side via the clutch 14. Theworking drum 6 is mounted at the machine frame 4. A reduction gear, forinstance, a planetary gear 24 may be arranged in the working drum 6,which decreases the speed of the belt pulley 13 on the drum side in aratio of, for instance, 1:20. The working drum 6 can thus work at aworking speed of approximately 100 rpm when the combustion engine 10 isoperated at a speed of, for instance, 2000 rpm, and the tractionmechanism 12 has a gear ratio of 1:1.

As can be seen from FIG. 3, the pump transfer case 16 is provided with,for instance, six hydraulic pumps 18 that are arranged in a circularmanner and with, for instance, the same mutual distance to one anotheraround the output shaft 22 of the drive train 8. A tensioning idler 32for the traction mechanism 12 is depicted in FIG. 3.

FIG. 4 shows a conventional, preferably hydraulically operated clutch14, with a braking device 19 additionally provided on the output side,which is capable of being additionally engaged immediately prior to,during or after switching of the clutch, and which may remain engageduntil the engagement of the clutch has ended. The braking device 19 actsbetween the drive shaft 21 and the output shaft 22.

The drive shaft 21 is connected to a clutch part element 34 in the formof an outer hollow ring with an inner toothing 35, which is permanentlyengaged in a form-fitting manner with an inner clutch part element 36with an outer toothing 37. Both clutch part elements 34, 36 may bedesigned as hollow rings. As can best be seen from FIGS. 4 and 6, theclutch part element 36 carries annular-shaped clutch linings 40 at theaxial front surfaces, which can be engaged with clutch elements 41, 42,43 on the output side by way of the coupling operation. An axiallymovable pressure piston 50 engages the movable clutch element 41, and isoperable to engage the clutch 14 by compressing elements 41, 42, 43against clutch linings 40.

As can further be seen from FIGS. 4 and 7, two clutch part elements 36movable in axial direction are provided in order to enable an increasedtorque transmission.

It is understood that more than two clutch part elements 36 or just onesingle clutch part element 36 may be provided as required. With apreferably hydraulic operation of the clutch 14, the axially movableclutch elements 41, 42 are pressed against the clutch linings 40 of theclutch part elements 36, with all parts jointly transmitting the forceto a clutch element 43 that is coupled to the output shaft 22.

FIG. 4 shows the clutch 14 in a switching position in which the clutchlinings 40 are not engaged yet, and the brake lining 23 of the brakingdevice 19 is already resting against the axial front surface of theouter clutch part element 34. It is understood that the brakingengagement may also take place after the engagement of the clutch. Inthat case, wear and tear of the brake lining 23 can be reducedsignificantly. It is essential that the toothing 35, 37 of the clutchpart elements 34, 36 rest against one another in, for instance, thedirection of the driving torque after the procedure of engaging theclutch, and are retained in that position by the braking device 19 evenif a non-load operation is taking place during critical operation at lowspeed. In that way, it is ensured that the toothing 35, 37 cannotvibrate, for instance, in non-load operation, which enables the wear andtear of this mechanical coupling of the clutch part elements occurringdue to the rotary vibrations can be reduced to a significant extent.

The arrangement of the braking device is not limited to the embodimentshown in FIG. 4; rather, it suffices that the braking device 19 actsbetween the drive side and the output side, thus precluding any playexisting in the mechanical coupling by fixing the elements involved intheir position so that they cannot move to and fro in relation to oneanother within the existing play due to the existing rotary vibrations.

When disengaging the clutch 14, the axially movable clutch elements 41and 42 are pushed apart by means of, for instance, six pressure springs38 that can be seen in FIG. 5, in which case the braking device 19,which is attached to the movable clutch element 41, with the brakelining 23 arranged at an annular flange 29 is also disengaged from theaxial front surface of the outer clutch element 34. The annular flange29 may be of an elastically deformable design in axial direction.

FIG. 4 shows a preferably hydraulically operated clutch 14 to which avibration damper 5 may be coupled on the output side that is fullydepicted in FIG. 6 in a cross-sectional view and in a top view.

The vibration damper 5 consists of several concentric rings, with afirst inner ring 25 being provided with a connecting device 28, forinstance, a connecting flange. The first ring 25 is surrounded by anelastic element 26 which, in the embodiment, entirely surrounds thefirst ring peripherally.

The second ring 27, which runs concentrically and coaxially to the firstring 25, serves as flywheel mass and is in turn firmly attached to theelastic element 26 peripherally.

FIG. 6 shows a radial arrangement of the first inner ring 25, theelastic element 26, and the outer second ring 27. It is understood,however, that an axial arrangement of these rings 25, 26, 27 is alsopossible. Furthermore, the flywheel mass does not necessarily have to beof annular shape, but may also consist of several individual flywheelmasses arranged symmetrically around the power-transmitting shaft.Furthermore, the first ring 25 may at the same time form the connectingdevice 28. Finally, a connecting device 28 not necessarily of annularshape may be provided in lieu of the first ring 25, which serves thepurpose of coupling to a power-transmitting shaft and is connected in anon-rotating manner to the elastic element 26. At least one flywheelmass is then attached to the elastic element in a non-rotating mannerand at a radial distance towards the outside.

The elastic element 26 may consist of an elastomer or else of metallicsprings, for instance, disc springs, leaf springs, or coil springs,which act in the direction of the rotary vibrations.

When using the elastic element 26 in a clutch 14, a rigidity of 35000Nm/rad to 45000 Nm/rad is preferred, with a value of 40000 Nm/rad havingproved to be particularly suitable. The relative damping value then isbetween 0.15 and 0.2, preferably 0.175.

Because of the inertia of the vibration damper 5, the flywheel mass ofthe same counteracts the rotary vibrations of the combustion engine 10,damping or eliminating the same.

Alternatively, radially acting brake linings 23 may be provided, as canbe seen from FIGS. 7 and 8, which when engaged rest against acircumferential surface of a clutch part element 34 on the drive side oroutput side.

FIG. 7 shows an embodiment with a braking device 19 that is capable ofradial operation, the brake linings 23 of which may, under the influenceof centrifugal forces, rest against an inner circumferential surface ofthe clutch part element 34, where the centrifugal force can be deflectedfrom the output shaft 22.

The braking device 19 is depicted in detail in FIG. 8. The brakingdevice 19 consists of an annular flange 70 which can be attached to, forinstance, a movable clutch element 41, with four brake shoes 76, as theyare in principle known from drum brakes, with radially outer brakelinings 23 being connected in an articulated and swivelling manner tothe annular flange 70 via coupling elements 72. Return springs 74 pullthe brake shoes 76 towards the inside radially if there is nocentrifugal force. During rotation of the output shaft 22, a centrifugalforce is created with increasing speed, so that the brake shoes 76 arepressed towards the outside radially against the clutch part element 34counteracting the force of the return springs 74.

The coupling elements 72 are aligned in such a manner that self-lockingoccurs in case of a brake engagement.

Although a preferred embodiment of the invention has been specificallyillustrated and described herein, it is to be understood that minorvariations may be made in the apparatus without departing from thespirit and scope of the invention, as defined by the appended claims.

1. A method of operating a construction machine, the constructionmachine having a machine frame, a working drum supported from themachine frame, a combustion engine supported from the machine frame, adrive train connecting the combustion engine and the working drum, thedrive train including a clutch, the clutch including a drive sideincluding at least one drive side clutch element and an output sideincluding at least one output side clutch element operably engageablewith the at least one drive side clutch element, the method comprising:(a) transferring a load torque from the engine to the working drumduring a working mode when the working drum is working a ground surface;(b) transferring a drag torque from the engine to the working drumduring a non-working mode when the working drum is rotating but notworking a ground surface; and (c) during engagement of the clutch,transmitting a braking torque between the output side of the clutch andthe drive side of the clutch without passing the braking torque throughthe operably engaged clutch elements, the braking torque being smallerthan the load torque and larger than the drag torque.
 2. The method ofclaim 1, wherein: the at least one drive side clutch element or the atleast one output side clutch element includes an axially fixed part andan axially slidable part engaged with one another via a mechanicalcoupling having rotational play between the axial fixed and axiallyslidable parts about a rotational axis of the clutch, and in step (c)the braking torque eliminates or reduces relative rotational motionbetween the axially fixed part and the axially slidable part caused bythe rotational play between the axially fixed part and the axiallyslidable part.
 3. The method of claim 1, wherein: the clutch includes anannular flange elastic in axial direction and connected to either thedrive side or the output side of the clutch, the other of the drive sideor the output side of the clutch includes an axial resting surface, andstep (c) further comprises frictionally engaging the annular flange withthe axial resting surface to transmit the braking torque.
 4. The methodof claim 3, further comprising: engaging the clutch by axially movingthe at least one output side clutch element with a hydraulic piston, andwherein the movement of the hydraulic piston also engages the annularflange with the axial resting surface.
 5. The method of claim 1,wherein: the clutch includes a plurality of radially acting brakelinings, and step (c) further comprises using centrifugal forces actingon the radially acting brake linings during rotation of the clutch totransmit the braking torque.
 6. The method of claim 1, furthercomprising: engaging the clutch by axially moving the at least oneoutput side clutch element with a hydraulic piston.
 7. The method ofclaim 1, wherein: in step (c) the braking torque is transmitted via anelectromagnetic force.
 8. The method of claim 1, wherein: in step (c)the braking torque is transmitted via an eddy current force.
 9. A methodof operating a construction machine, the construction machine including:a machine frame; a working drum supported from the machine frame; acombustion engine supported from the machine frame; and a drive trainconnecting the combustion engine and the working drum so that thecombustion engine drives the working drum, the drive train including adrive shaft, an output shaft and a clutch arranged between the driveshaft and the output shaft, the clutch including: a drive side includingat least one drive side clutch element; an output side including atleast one output side clutch element operably engageable with the atleast one drive side clutch element to rotationally couple the driveshaft and the output shaft; wherein the at least one drive side clutchelement or the at least one output side clutch element includes anaxially fixed part and an axially slidable part engaged with one anothervia a mechanical coupling having rotational play between the axial fixedand axially slidable parts about a rotational axis of the drive shaft;the method comprising the steps of: transmitting via a clutch brake africtional rotating force between the drive side and the output sidewithout passing the frictional rotating force through the operablyengaged clutch elements, and thereby reducing relative rotational motionbetween the axially fixed part and the axially slidable part caused bythe rotational play between the axially fixed part and the axiallyslidable part.
 10. The method of claim 9, further comprising:transferring a load torque from the engine to the working drum during aworking mode when the working drum is working a ground surface;transferring a drag torque from the engine to the working drum during anon-working mode when the working drum is rotating but not working aground surface; and wherein the frictional rotational coupling forceprovided by the clutch brake during the transmitting step is such that abraking torque transferred from the output shaft to the drive shaft viathe clutch brake is smaller than the load torque and larger than thedrag torque.
 11. The method of claim 9, wherein: the frictionalrotational coupling force provided by the clutch brake is such that abraking torque transferred between the output shaft and the drive shaftvia the clutch brake is smaller than a maximum torque in a firstrotational direction transferred from the drive shaft to the outputshaft to rotate the working drum when the working drum is engaging aground surface, and the braking torque is larger than any torquetransferred from the output shaft back to the drive shaft in a secondrotational direction opposite the first rotational direction due torotational vibration of the drive train.
 12. The method of claim 9,wherein: the frictional rotational coupling force provided by the clutchbrake is such that a braking torque required to overcome the frictionalrotational coupling force to rotationally move the axially fixed partrelative to the axially slidable part within the rotational playtherebetween is larger than a maximum torque transferred from the driveshaft to the output shaft to rotate the working drum when the workingdrum is in non-load operation not engaging a ground surface.
 13. Themethod of claim 9, wherein: the frictional rotational coupling forceprovided by the clutch brake couples the axially fixed part and theaxially slidable part sufficiently to eliminate the rotational playtherebetween at least in the rotational direction of load transfer fromthe drive shaft to the output shaft.
 14. The method of claim 9, wherein:the clutch brake includes an annular flange elastic in axial directionand connected to either the drive side or the output side of the clutch,the other of the drive side or the output side of the clutch includes anaxial resting surface, and the transmitting step further comprisesfrictionally engaging the annular flange with the axial resting surfaceto transmit the frictional rotating force.
 15. The method of claim 14,further comprising: engaging the clutch by axially moving the at leastone output side clutch element with a hydraulic piston, and wherein themovement of the hydraulic piston also engages the annular flange withthe axial resting surface.
 16. The method of claim 9, wherein: theclutch includes a plurality of radially acting brake linings, and thetransmitting step further comprises using centrifugal forces acting onthe radially acting brake linings during rotation of the clutch totransmit the frictional rotating force.
 17. A construction machine,comprising: a machine frame; a working drum supported from the machineframe; a combustion engine supported from the machine frame; and a drivetrain connecting the combustion engine and the working drum so that thecombustion engine drives the working drum, the drive train including adrive shaft, an output shaft and a clutch arranged between the driveshaft and the output shaft, the clutch including: a drive side includingat least one drive side clutch element; an output side including atleast one output side clutch element operably engageable with the atleast one drive side clutch element to rotationally couple the driveshaft and the output shaft; wherein the at least one drive side clutchelement or the at least one output side clutch element includes anaxially fixed part and an axially slidable part engaged with one anothervia a mechanical coupling having rotational play between the axial fixedand axially slidable parts about a rotational axis of the drive shaft;and wherein the drive train further includes an electromagnetic clutchbrake operable during engagement of the clutch to provide a rotationalcoupling force between the drive side and the output side to eliminateor reduce relative rotational motion between the axially fixed part andthe axially slidable part caused by the rotational play between theaxially fixed part and the axially slidable part, the clutch brake beingseparate from the clutch elements so that the rotational coupling forceof the clutch brake is transmitted between the drive side and the outputside without passing through the operably engaged clutch elements.
 18. Aconstruction machine, comprising: a machine frame; a working drumsupported from the machine frame; a combustion engine supported from themachine frame; and a drive train connecting the combustion engine andthe working drum so that the combustion engine drives the working drum,the drive train including a drive shaft, an output shaft and a clutcharranged between the drive shaft and the output shaft, the clutchincluding: a drive side including at least one drive side clutchelement; an output side including at least one output side clutchelement operably engageable with the at least one drive side clutchelement to rotationally couple the drive shaft and the output shaft;wherein the at least one drive side clutch element or the at least oneoutput side clutch element includes an axially fixed part and an axiallyslidable part engaged with one another via a mechanical coupling havingrotational play between the axial fixed and axially slidable parts abouta rotational axis of the drive shaft; and wherein the drive trainfurther includes an eddy current clutch brake operable during engagementof the clutch to provide a rotational coupling force between the driveside and the output side to eliminate or reduce relative rotationalmotion between the axially fixed part and the axially slidable partcaused by the rotational play between the axially fixed part and theaxially slidable part, the clutch brake being separate from the clutchelements so that the rotational coupling force of the clutch brake istransmitted between the drive side and the output side without passingthrough the operably engaged clutch elements.